APi request problem with coinApi.io

[dal]

Hi all, so I'm quite new to this api stuff.
Im trying to get some bitcon exchange data from coinApi using flutter / dart and I keep getting a response 401
So I'm fairly sure it's the url that I'm sending is wrong in some way but I just can't work out the full URL should be. As you
can probably tell I'm trying to get back the cost of 1 bitcoin in USD, I will want to get it in other currencies as well.
Could someone please take a look at the link below and tell me what I should be sending.
Thanks

coinapi

EDIT : I've sorted it
I should have parsed this : https://rest.coinapi.io/v1/exchangerate/BTC/USD?apikey=$apiKey
basically missed the ? out ( doh )

this is my code

import 'package:http/http.dart' as http;


const coinAPI2 = 'https://rest.coinapi.io/v1/exchangerate/BTC/USD';
const apiKey = 'MY API KEY'; // obviously I am using my actual api key

class CoinData {
 
  Future getCoinData() async {
    var url = Uri.parse('$coinAPI2$apiKey');

    http.Response response = await http.get(url);

    if (response.statusCode == 200) {
      print(response.body);
    } else {
      print('response  was  ${response.statusCode}');
    }
  }
 
}